How do I prevent TB to fetch the contents of PDFs when dragging 'n dropping from Devonthink

Yes

After creating the TOC document in DEVONthink, which is an RTF, I suggest selecting all of its text and changing the List style to “none” so that the contents no longer is indicated with “1.”, “2.”, etc., Then copy and paste the TOC into a Tinderbox note. Afterward, you can explode the note to get a new note for every TOC entry and use a stamp to set $URL=$Text. Note: this stamp will not work. I’ll post one that does, later.

If you do not need a lot of notes, then it also works to select a URL in a Tinderbox note and drag the URL into the Outline, which creates a new note with $URL linking back to DEVONthink.